TEMPERATURE COEFFICIENT
OF THE
CERIC - GEROUS ELECTRODE

by
R ichard B e ll S a l t o n s t a l l

A THESIS
P r e s e n t e d to th e G rad u ate School of M ichigan
• C o lleg e o f A g r ic u ltu r e and A pplied
S cien ce in P a r t i a l F u l f i l l m e n t
o f R e q u ire m e n ts f o r the
Degree of
D octor o f P hilosophy

C hem istry D epartm ent
E a s t L a n sin g , M ichigan
1955

-

1

-

INTRODUCTION
Compounds o f e e r i e c e r i u m h a v e
unusual oxid izin g p ro p e rtie s .
proceed q u ickly

In a c i d s o l u t i o n s ,

to c o m p le tio n and u s u a l l y i n

secondary changes.
be p o s s i b l e

been p r o v e n to have r a t h e r
such r e a c tio n s

th e a b s e n c e o f any

B e c a u s e o f t h e s e two p r o p e r t i e s

to e v a l u a t e r a t h e r a c c u r a t e l y

it

should

th e change in f r e e

en erg y accom panying a r e a c t i o n w h e re in th e cerium io n u n d erg o es
a v alence

change.

The p o t e n t i a l o f t h e

c e r i c - c e r o u s e l e c t r o d e h as been m eas­

u r e d by B a u e r a n d G l a e s s n e r
Gj 5 3 4 ,

( l % 0 3 ) , a n d by Kunz ( K u n z ,

(1931),

iate

J . Am. Chem. S o c . ,

A norm al calom el e le c tr o d e

and s a t u r a t e d p o ta ssiu m c h lo r id e
e lectro ly te .

fu lly

Z .E lektrochem .,

The m e a s u r e m e n t s o f B a u e r a n d G l a e s s n e r w e r e

room t e m p e r a t u r e ,
ence,

(Bauer and G la e s s n e r ,

The a c i d i t y

c o n tro lled .

one t e m p e r a t u r e ,

made

at

was u s e d f o r r e f e r ­

o f t h e s o l u t i o n s was n o t c a r e ­
l i m i t e d the ac c u ra c y

The m e a s u r e m e n t s o f Kunz w e r e made a t o n l y

25°C.

± 0 .0 1 °,

a g a i n s t a hydrogen e le c tr o d e

s u l f u r i c a c i d s o l u t i o n o f t h e same c o n c e n t r a t i o n a s
cerium h a l f - c e l l s .

98,

s o l u t i o n as an in te rm e d ­

These f a c t o r s s e r i o u s l y

o f th e m easurem ents.

53,

in

t h a t i n the

Two c o n c e n t r a t i o n s o f a c i d w e r e u s e d ; - 0 . 5

fo rm a l and 1 .0 f o rm a l.

A f l o w i n g j u n c t i o n was e m p l o y e d t o m a i n ­

ta in a co n stan t liq u id - liq u id p o te n tia l.
•Because o f th e s o l u b i l i t i e s

o f e e r i e a n d c e r o u s ammonium

su lfates,

and b ecau se o f th e s t a b i l i t y

sa lts,

was d e c i d e d t o d e t e r m i n e

it

of s o lu tio n s of these

the p o t e n t i a l o f the c e r ic -

cerous e l e c t r o d e u s in g th e s e double s a l t s

98856

o f cerium ,

and

to

e x ten d the

te m p e ra tu re range o f the m easurem ents,

sin ce

the

te m p e r a tu r e c o e f f i c i e n t o f the e l e c t r o d e has n o t been p r e v i ­
o usly d e term in e d .
The p u r p o s e s o f t h i s

i n v e s t i g a t i o n were,

then,

to m easure

the p o t e n t i a l of the c e r i c - c e r o u s e l e c t r o d e

in s u lf u r ic

so lu tio n ,

- e e r i e and cerous

u t i l i z i n g double s a l t s

ammonium s u l f a t e s ;

to d e te rm in e

o f cerium ,

t h e e f f e c t o f t h e ammonium

s u l f a t e upon the p o t e n t i a l o f the e l e c t r o d e ;
te m p e ra tu re c o e f f i c i e n t o f the e l e c t r o d e ,
to c a l c u l a t e

acid

to d e te rm in e

the

an d from t h e s e d a t a

th e d e c r e a s e i n f r e e en erg y and d e c r e a s e in h e a t

c o n te n t f o r the r e a c t i o n

Ce1 , , , + e — * Ce1'•

The c e l l m e a s u r e d w a s ; 2(NH4 ) 2 S04 . C e ( S 0 4 ) 2 ( c " )
P t+ H 2 ,H 2 S04 ( 0 . 5 f ) ,HgS04 ( 0 . 5 f ) + (NH^ )
(g ,^ ) ^ ( c .)
There a r e

th re e sources of p o te n t ia l in th is

t i a l o f the hydrogen e l e c t r o d e ,
ju n ctio n ,

the p o te n ­

the p o t e n t i a l o f the

liq u id

and the p o t e n t i a l o f the c e r i c - c e r o u s e l e c t r o d e .

making th e c o n c e n t r a t i o n o f s u l f u r i c
equal,

cell;-

By

a c id in both h a l f - c e l l s

a n d by k e e p i n g t h e c o n c e n t r a t i o n o f t h e c e r i u m

salts

v ery s m a ll in com parison w ith t h a t o f the s u l f u r i c a c i d ,

the

p o t e n t i a l o f t h e l i q u i d j u n c t i o n was made n e g l i g a b l y s m a l l .
APPARATUS

AND

MATERIALS

The c e l l was a m o d i f i c a t i o n o f one u s e d i n t h i s
a t o r y by L a r s o n
u rin g a c t i v i t i e s
cell,

(Larson,

T h e s i s , M. S . C.

(1931)

lab o r­

in meas­

o f s o l u t i o n s of hydrobrom ic a c i d . Each h a l f ­

c o n s t r u c t e d from p y r e x t u b i n g ,

c l o s e d by a g r o u n d g l a s s s t o p p e r

(P ig . 1, a ,

b .)

was

(h) b e a r i n g a p l a t i n u m e l e c -

>
a S W 3 j|

4

-

trode

(e).

A jet

(c)

-

e n te r e d a t th e bottom o f each h a l f ­

c e l l to p erm it s a t u r a t i o n o f the l i q u i d w ith g a s .

Two

c e r i u m h a l f - c e l l s w e r e c o n n e c t e d t o on e h y d r o g e n h a l f - c e l l
thro u g h a flo w in g j u n c t i o n
S o c ,, 42,
on t h e

229,

(1920).

(f)

(Lamb a n d L a r s o n ,

Stopcocks

top and bottom edges o n ly ,

(i)

J . Am.Chem.

were g r e a s e d

lig h tly

in o rd e r t h a t a good e l e c ­

t r i c a l c o n t a c t m i g h t be m a i n t a i n e d t h r o u g h o u t t h e c e l l w i t h ­
out stopcock leak ag e.
through th e

trap s

The g a s e s e s c a p e d f r o m t h e h a l f - c e l l s

(d),

■ C e r i c a n d c e r o u s ammonium s u l f a t e s

c o r r e s p o n d i n g -to t h e

form ulas
2(KH4 ) 2 S ° 4 . C e ( s 0 4 ) 3 . 2H2 °
(NH4 ) g S04 . Oe2 ( S 0 4 ) 3 . 8H20
w e r e p r e p a r e d e s p e c i a l l y f o r t h i s w o r k ( P r e p a r e d by O s c a r T.
C o ffelt,

Jackson, M ich .).

A good g rad e o f c o n d u c tiv ity w ater

was u s e d i n m a k i n g s o l u t i o n s .

T h i s was h e a t e d a n d e v a c u a t e d

im m e d i a t e l y b e f o r e u s e i n o r d e r t o remove any oxygen o r o t h e r
g a s e s w hich m ig h t i n t e r f e r e

w ith the p o t e n t i a l ,

or cause o x i­

d a tio n o r r e d u c tio n in th e cerium h a l f - c e l l s .
T e m p e r a t u r e was c o n t r o l l e d by two t h e r m o s t a t i c w a t e r b a t h s ,
one b e i n g h e l d c o n s t a n t a t 2 5 ° C . dkO.Ol0 , t h e o t h e r b e i n g o p e r o
o
a t e d a l t e r n a t e l y a t 15 a n d 35 C.
Hydrogen
electro ly sis

for

the

h y d r o g e n e l e c t r o d e was g e n e r a t e d

o f a 1% s o l u t i o n o f s o d i u m h y d r o x i d e b e t w e e n

n ic k e l gauze e le c tr o d e s .

The g a s was p a s s e d o v e r a h e a t e d

p l a t i n u m s p i r a l t o remove oxygen,, and t h r o u g h a s a t u r a t o r
fore

en terin g

by

the hydrogen h a l f - c e l l .

be­

Tank n i t r o g e n was p u r i f i e d by b u b b l i n g t h r o u g h a n a l k a l i n e
p y ro g allo l so lu tio n ,

washing w ith w a te r ,

and p a ssin g over

h e a te d co p p er gauze in a com bustion f u r n a c e .

a

The g a s was

p a s se d th ro u g h a s a t u r a t o r b e f o re e n te r in g s th e cerium h a l f ­
cell.
H ydrogen e l e c t r o d e s were p r e p a r e d a c c o r d i n g to
tio n s

o f P o p o f f , Kunz a n d Snow ( P o p o f f , K u n z ,

Chera., 10 59,

the d i r e c ­

a n d Snow, J . P h y s .

( 1 9 2 8 ), w ith th e e x c e p t i o n t h a t th e y were n o t g o l d

plated .
P o t e n t i a l was m e a s u r e d t o 0 . 0 0 0 0 1 v o l t s
Queen S t a n d a r d p o t e n t i o m e t e r m o d e l E - 3 0 4 0 ,

by m ean s o f

a

in c o n ju n c tio n w ith

a L e e d s a n d N o r t h r u p Type R g a l v a n o m e t e r , No. 250QP. The g a l ­
vanom eter,

po ten tio m eter,

and c e l l s ,

w e r e s h i e l d e d a n d p u t on a n e q u i p o t e n t i a l b a s e ,

co rd in g to

t h e s y s t e m o f W. P . W h i t e

S o c . , 36,

2011,

(1914).

working b a t t e r y ,

th erm o static baths,
ac-

(W. P . W h i t e , J . Am. Chem.

The s t a n d a r d o f e . m . f .

was a n E p p l e y

s t a n d a r d c e l l w h i c h was m e a s u r e d a n d c e r t i f i e d by t h e U. S.
Bureau o f S ta n d a rd s .

T h i s c e l l was i m m e r s e d i n t h e 2 5 °

bath

in a w a te rp ro o f bo*.
ANALYTICAL

METHODS

A n a l y s i s o f C e r i u m S o l u t i o n s ; - The p r i m a r y s t a n d a r d u s e d i n
a l l c e r i u m a n a l y s i s was

B u reau o f S t a n d a r d s sodium o x a l a t e ,

d r i e d i n t h e o v e n f o r one h o u r a t 1 2 0 ° C f
of eerie

su lfate,

A stan d ard so lu tio n

ab o u t 0.01 N (w eig h t n o rm a lity )

was s t a n ­

d a r d i z e d a g a i n s t sodium o x a la te ., u s i n g t h e m ethod o f

W alden,

H a m m e t t,

J.

a n d Chapman ( W a l d e n , H a m m e t t ,

a n d Chapman,

Am.

-

Chem.

S o c . , £35, 2 6 4 9 ,

a l l analyses.

6

-

(1933).

W eight b u r e t t e s were u s e d i n

A q u a n t i t y o f f e r r o u s ammonium s u l f a t e

so lu ­

t i o n a b o u t 0 . 0 1 N. was p r e p a r e d a n d s t o r e d u n d e r h y d r o g e n t o
p r e v e n t o x i d a t i o n by the a i r .
some o x i d a t i o n o c c u r r e d ,
so lu tio n
fate

In s p i t e

of th is p recau tio n ,

a n d t h e f e r r o u s ammonium s u l f a t e

was c h e c k e d d a i l y a g a i n s t t h e s t a n d a r d e e r i e s u l ­

so lu tio n .
Some o r t h o - p h e n a n t h r o l i n e - f e r r o u s c o m p l e x i n d i c a t o r was

prepared,

fo llo w in g the d i r e c t i o n s

Chapman ( r e f .

above)

and t h i s

o f Y/al den ,

H a m m e tt , a n d

i n d i c a t o r was u s e d i n a l l

cerium

an aly sis.
Two 14 m l . p o r t i o n s w e r e w i t h d r a w n f r o m e a c h c e r i u m h a l f ­
c e ll for an aly sis,
added 0 .6 m l.

and w e ig h e d i n 125 m l. f l a s k s .

of concentrated s u lf u r ic a c id .

e a c h h a l f - c e l l was t h e n t i t r a t e d
ium s u l f a t e

I).

To e a c h was

One p o r t i o n f r o m

d i r e c t l y w i t h f e r r o u s ammon­

s o l u t i o n to d eterm in e

the e e r i e c o n te n t

(see note

The o t h e r p o r t i o n s w e r e o x i d i z e d w i t h ammonium p e r s u l f a t e

usin g s i l v e r n i t r a t e
Chem. S o c . ,

50,

cerium c o n t e n t .

Note I .

as a c a t a l y s t

1322 an d 1379,

( W i l l a r d a n d Y o u n g , J . Am.

(1928),

to d eterm in e th e t o t a l

The c e r o u s c o n t e n t was f o u n d by d i f f e r e n c e .

A ll cerium c o n c e n tr a tio n s u n le s s s p e c i f i c a l l y

oth erw ise,

stated

a re e x p re s s e d in m illim o le s of cerium p e r th o u san d

grams o f s o l u t i o n .

i.AX»X*a/

,

-

7

-

A n a l y s i s of_ S u l f u r i c A c i d S o l u t i o n s : - T h i s a n a l y s i s was a c ­
c o m p l i s h e d by a d i r e c t t i t r a t i o n
m ethyl orange i n d i c a t o r .
ly to th e end p o i n t,
oxide,

w i t h sodium c a r b o n a t e , u s i n g

The t i t r a t i o n was c a r r i e d o u t n e a r ­

th e s o l u t i o n b o i l e d to e x p e l carbon

c o o le d , and th e t i t r a t i o n

com pleted.

d i­

The s o d i u m c a r b o n ­

a te u sed i n t h i s a n a l y s i s had been e s p e c i a l l y p re p a re d

from

s o d i u m b i c a r b o n a t e by h e a t i n g t o 3 0 0 ° G .
PREPARATION

OP

SOLUTIONS

S u l f u r i c A c i d S o l u t i o n s : - C. P .

s u l f u r i c a c i d was d i l u t e d t o

make a l a r g e q u a n t i t y o f a p p r o x i m a t e l y 5 0 $ a c i d .
s to re d in a larg e g la ss

stopp ered

b o ttle.

T h i s was

A p o rtio n of th is

a c i d was w e i g h e d c a r e f u l l y a n d d i s s o l v e d i n a w e i g h e d q u a n t i t y
of evacuated d i s t i l l e d
im ately 0 .5

w a t e r t o make a b o u t a l i t e r

form al a c id .

m ethod g i v e n a b o v e .

T h i s was c a r e f u l l y a n a l y z e d by t h e

Prom t h i s

th e e x a c t w eight o f the

of approx­

d e t e r m i n a t i o n was

50 $ a c i d

calcu lated

t o be a d d e d t o a t h o u s a n d

g r a m s o f w a t e r t o make a s o l u t i o n e x a c t l y 0 . 5 f o r m a l .

Subse­

q u e n t a n a l y s e s o f t h e 0 . 5 f o r m a l a c i d made u p by t h i s m e t h o d
proved t h a t th e c o n c e n tra tio n of the a c id
t h a n one p a r t

d i d n o t v a r y more

in a th o u san d . About 4000g. o f 0 .5 fo rm al acid,

was made u p a t a t i m e .
C e r i c - c e r o u s Ammonium S u l f a t e
p o r tio n s o f the c r y s t a l l i n e

w eighed

c e r i c a n d c e r o u s ammonium

f a t e s were a n a l y z e d to d e te r m in e
co ntents,

s o l u t i o n s ; - sm all

su l­

th e c e r i c and t o t a l cerium

and the q u a n t i t i e s n e c e s s a r y

t o make s o l u t i o n s

th e d e s i r e d c o n c e n tr a tio n s o f c e r i c and c e ro u s s a l t s

of

were

-

dissolved, d i r e c t l y
utions

8

-

in th e 0 .5 form al s u l f u r i c a c id ,

The s o l ­

th u s form ed were a ll o w e d to s t a n d o v e r n i g h t i n

to a llo w any p o s s i b l e

in so lu b le

p artic le s

t o s e t t l e , . The s o l ­

u t i o n s were d e c a n t e d u n d e r n i t r o g e n p r e s s u r e ,
the cerium h a l f - c e l l s .

order

and p la c e d

in

A b o u t 2 0 0 0 g . o f s o l u t i o n was made up

a t a tim e._
EXPERIMENTAL
Two u n i t s ,

METHODS

AND

CALCULATIONS

e a c h c o m p o s e d o f two c e r i u m h a l f - c e l l s

and

on e h y d r o g e n e l e c t r o d e w e r e f i l l e d a t a t i m e .
F illin g

th e Cerium H a l f - c e l l s ; -

The h a l f - c e l l was f l u s h e d

o u t f o r a tim e w i t h a slow s tr e a m o f n i t r o g e n .
the n itr o g e n

i n l e t tube and j e t ,

and th e c o rre s p o n d in g

o f t h e f l o w i n g j u n c t i o n -were r i n s e d

s e v e r a l tim es w ith

s o l u t i o n w i t h w h i c h t h e y w er e t o be f i l l e d ,
t i o n s b e i n g w i t h d r a w n by s u c t i o n .
fille d

to the p ro p e r l e v e l ,

The h a l f - c e l l ,
h alf
the

the r i n s i n g p o r ­

The h a l f - c e l l a n d t r a p w e r e

and the ground g l a s s s t o p p e r , b e a r ­

i n g a b r i g h t p l a t i n u m f o i l e l e c t r o d e was r i n s e d a n d p u t i n
p lace.

The t u b e l e a d i n g f r o m t h e t r a p was c l o s e d w i t h a r u b ­

ber plug,
up i n t o

and th e p r e s s u r e o f the n i t r o g e n f o r c e d the l i q u i d

the flo w in g ju n c tio n ,

s t o p c o c k was c l o s e d .
the

a t w hich p o i n t the th re e-w ay

The p l u g was i m m e d i a t e l y r e m o v e d f r o m

tr a p o u t l e t and s u b s t i t u t e d fo r the n itr o g e n tu b e,

sealin g

thus

th e h a l f - c e l l u n t i l th e o t h e r s were f i l l e d .

F i l l i n g s / The H y d r o g e n H a l f - c e l l s ; -

The h y d r o g e n

electrode

v e s s e l s w e r e f i l l e d w i t h 0 . 5 f o r m a l s u l f u r i c a c i d i n t h e same
manner as th e cerium h a l f - c e l l s ,

hydrogen being s u b s t i t u t e d

9

-

-

for nitrogen.
The s a t u r a t o r s w e r e f i l l e d , w i t h t h e same s o l u t i o n s ,
sp ectiv e ly ,

c o n n e c te d to th e gas i n l e t tu b e s of th e h a l f - c e l l s ,

a n d t h e w ho se a s s e m b l y p l a c e d i n t h e 1 5 ° t h e r m o s t a t .
f l o w was r e g u l a t e d by m e a n s o f s m a l l p i n c h c l a m p s ,

The g a s

the h y d ro ­

gen so t h a t i t p a s s e d th ro u g h th e s o l u t i o n a t th e r a t e
on e b u b b l e p e r s e c o n d ,

and the n itr o g e n a t th e r a t e

o n e b u b b l e e v e r y two o r t h r e e
were to e x c lu d e a i r ,

seconds,

of about

of about

only fu n c tio n s

th e s o l u t i o n in the

The s e p a r a t o r y f u n n e l s w h i c h s u p p l i e d t h e

to th e f lo w in g j u n c t i o n s were f i l l e d

The w a s t e t u b e s w e r e c o n n e c t e d
(F ig.

since i t s

and to g e n tly a g i t a t e

cerium h a l f - c e l l s .
liq u id s

re­

and p u t i n p l a c e .

to t h e flow ing: j u n c t i o n o u t l e t s ,

1 , g) w h i c h c o m p l e t e d t h e p r e l i m i n a r y p r o c e d u r e f o r t h e

m easurem ent o f th e e . m . f .

o f the c e l l s .

E a c h o f t h e s o l u t i o n s was a n a l y z e d f o r t h e c e r i c a n d t h e
cerous c o n te n t.
M e a s u re m e n ts ; - W ith th e s m a l l h y d ro g e n e l e c t r o d e v e s s e l s ,
s i s t e n t m e a s u r e m e n t s c o u l d b e made a n h o u r a f t e r p l a c i n g
cells

in the

therm ostat.

W ith th e

larg er v essels,

h o u r s e l a p s e d b e f o r e e q u i l i b r i u m was r e a c h e d ,
i t was f o u n d t o b e a d v i s a b l e
flow o f h y d ro g en .

in crease

of eq u ilib riu m .

case

the r a t e

By m e a n s o f a b r i d g e ,

of

over

t h e two

c o u l d be m e a s u r e d a g a i n s t e a c h o t h e r ,

t h i s was d o n e o c c a s i o n a l l y ,
sta te

and in t h i s

in o rd e r to d e f i n i t e l y e s t a b l i s h

the h a l f - c e l l s .

hydrogen e le c tr o d e s

the

several

The c e l l s w e r e m e a s u r e d a t i n t e r v a l s

a tw enty-four hour p erio d ,
eq u ilib riu m in

to s l i g h t l y

con­

t o make s u r e

and

t h a t b o th were i n a

....

-

10

-

At th e end o f a p p r o x im a te ly

tw enty-four hours,

two p o r ­

t i o n s w e r e w i t h d r a w n f r o m one o f t h e c e r i u m h a l f - c e l l s ,
analyzed according

to th e p ro ced u re

w e r e t h e n mo ve d i n t o
fore.

o u tlin e d above.

th e 25° t h e r m o s t a t ,

and

The c e l l s

and m easured a s b e­

The f l a w i n g j u n c t i o n s w e r e o p e r a t e d o n l y a s h o r t p e r i o d

o f tim e b e fo re

r e a d i n g s were t a k e n .

Due t o t h e l o n g p e r i o d

o f tim e o v e r which th e c e l l s were m e a s u re d , a p r o h i b i t i v e
q u an tity

o f s o l u t i o n would h ave b een n e c e s s a r y ,

tio n s been o p erated c o n tin u o u sly .

had the ju n c ­

\7h.ile i n o p e r a t i o n ,

t i o n flow ed th ro u g h th e j u n c t i o n s a t a r a t e

so lu ­

o f a b o u t one d r o p

of each liq u id p e r second.

o
W h i l e t h e c e l l s w e r e b e i n g m e a s u r e d a t 25 , t h e t e m p e r ­
ed
a t u r e o f t h e 15 t h e r m o s t a t was r a i s e d by m ea n s o f a u x i l i a r y
h eaters

t o 3 5 ° , a n d a" t h e - r r n o r e g u l a t o r a n d Beckmann t h e r m o m e t e r

w hich had been s e t a t 35° were s u b s t i t u t e d
15°.

fo r those s e t a t

The b u l b s o f t i e ' l a t t e r w e r e im m e r s e d i n c o l d r u n n i n g

w a te r u n t i l needed in o rd e r to keep

them s e t a t

the p r o p e r

tem perature.
When t h e c e l l s h a d b e e n m e a s u r e d o v e r t h e
h o u r p>eriod a t 2 5 ° ,

tw en ty -fo u r

p o r t i o n s were w ith d ra w n from a n o t h e r

cerium h a l f - c e l l and a n a ly z e d as b e f o r e .

The c e l l s w e r e

th e n p l a c e d i n th e 35° t h e r m o s t a t where th e m easurem ents
were r e p e a t e d .

I n a s m u c h a s m e a s u r e m e n t s w e r e m ore d i f f i c u l t

a t t h i s h ig h e r tem p eratu re,

and t h e ch ange i n r a t i o w i t h i n

t h e c e r i u q i h a l f - c e l l s was a c c e l e r a t e d ,
to r e s e r v e

two h a l f - c e l l s

i t was t h o u g h t b e s t

for a n aly sis a t th is

tem perature.

11

-

-

E ach tim e c e l l s were m e a s u re d ,
o f t h e Bec kmann t h e r m o m e t e r ,

the d a t e ,

barom eter,

tim e,

reading

and te m p e ra tu re o f

th e b a r o m e t e r were r e c o r d e d .
C a l c u l a t i o n o f th e Tem perature and P r e s s u r e C o r r e c tio n s f o r
th e Hydrogen E l e c t r o d e ; - For c l a r i t y ,

l e t us add to th e

hydrogen e le c tr o d e o f the o x id a tio n - r e d u c tio n c e l l ,
sure c e l l

co n sistin g

0.5 form al s u l f u r i c
atm osphere,

o f two h y d r o g e n e l e c t r o d e s ,
acid,

latter,

and the o th e r ,

f o r example-,

both in

o n e b e i n g u n d e r a p r e s s u r e o f one
connected to the hydrogen e le c tr o d e

of the o x id a tio n - r e d u c tio n c e l l ,
the

a pres­

u n d e r t h e same p r e s s u r e a s

740 ram. o f m e r c u r y ;

t h e two c e l l s

may t h e n b e w r i t t e n a s f o l l o w s :
P t H ( l ) , H ( 0 . 5 f X a ) , H (740/760) P t P t H J 7 4 0 / 7 6 0 ) .
. .P t
2
q
2
2
A s s u m i n g t h a t two f a r a d a y s o f p o s i t i v e e l e c t r i c i t y a r e p a s s e d
th ro u g h the p r e s s u r e

ceil

|-H2 ( 1 )

to the r i g h t , t h e

change in s t a t e

- e — > H * ( 0 . 5 f X a)

H * ( 0 .5 f X a) + e — * £ H 0 ( 740/760)
£H2 ( 1 ) •— » ^H2 ( 7 4 0 / 7 6 0 )
S u b stitu tin g

in the N e rn st e q u a tio n :
1

E -E

or,

q

- RT I n
NF

(740/760 V

a t 25°C .:
E= ^E0 -

.0591
2

log

(740/760)

E -0 .0 0 0 3 4 v o l t s .
This i s

the

te m p e ra tu re and piressure c o r r e c t i o n f o r the

is:

12

hydrogen e l e c t r o d e ,

t o he a d d e d t o t h e m e a s u r e d E o f t h e

id atio n -red u ctio n c e ll.
w er e c a l c u l a t e d ,

-

Three s e r i e s

one f o r e a c h o f t h e

ox­

of these c o rre c tio n s
three

tem p eratu res used

i n t h e ” m e a s u r e m e n t s , a t p r e s s u r e s r a n g i n g b e t w e e n 690 mm.and
760 mm. o f m e r c u r y ,
(F ig.

and t h e s e were i n c o r p o r a t e d i n a g r a p h

2;) f r o m w h i c h t h e c o r r e c t i o n s

c o u l d be q u i c k l y d e t e r ­

mined a s so o n as t h e p a r t i a l p r e s s u r e s o f th e h y d ro g e n i n
t h e h a l f - c e l l s w e r e kno wn.
These p a r t i a l p r e s s u r e s o f h y d r o g e n were c a l c u l a t e d a s
s u g g e s t e d by E l l i s
The v a p o r p r e s s u r e s

(E llis,

J.

Am. Chem. S o c . , 3 8 ,

of 0 .5 form al s u lf u r ic

737,

acid a t

(1916).

the t h r e e

t e m p e r a t u r e s were i n t e r p o l a t e d from d a t a g iv e n i n th e I n t e r ­
n a t i o n a l C r i t i c a l T ab les
The v a p o r p r e s s u r e

(I.

C.

T. V o l .

Ill,

p . 303).

o f t h e s u l f u r i c a c i d was s u b t r a c t e d

from th e b a r o m e t r i c p r e s s u r e

corrected

to 0°C.

To t h i s was

ad d ed th e m e rc u ry e q u i v a l e n t o f th e column o f l i q u i d i n t h e
h alf-cell,
the s u rf a c e

m easu red from th e m iddle o f th e p la tin u m f o i l
of the

to

l i q u i d , a n d the m ercury e q u i v a l e n t o f the

column o f s u l f u r i c a c i d i n

the t r a p . M ercury e q u i v a l e n t s o f

s u l f u r i c a c i d were c a l c u l a t e d from d e n s i t y d a t a i n th e I n t e r ­
n a t i o n a l C r i t i c a l T ables

(I.

C.

T. V o l . I l l ,

p.

156).

C a l c u l a t i o n o f the C e r i c - c e ro u s E l e c t r o d e C o r r e c t i o n s : The r e a c t i o n w h i c h w o u l d o c c u r i n t h e c e r i u m h a l f - c e l l
one f a r a d a y o f p o s i t i v e e l e c t r i c i t y

if

was p a s s e d t o t h e r i g h t

is:
Ce • " ' ( c" X a " ) -V- e — > C e " ' ( c '

Xa')

-

13

-

720

(mo.

of mercury

at 0 ° q#

7cO

pressure

35°

700

690

0002

000U
E (v o lts )

ELa;. ? .

0006

ooos

to be added to E o f c e l l

P r e s s u r e and te m p e ra tu re c o r r e c tio n s f o r
hydrogen e le c tr o d e .

0010

0012

-

S u b stitu tin g

14

-

in the H e rn st e q u a tio n :
Eo ~ M
NF
E=E

Cg..,..t * ( c f )
Ue r r » ' ( c* J

(Hote 2 )

- . 0 5 9 1 l o g Ce ' » »( c 1)
Ce ' ' * ’T c ^ )

C a l c u l a t i o n o f - A F a nd - AH:

at

By e x t r a p o l a t i n g

25°C.

to z e r o ,

the

e . m . f . v a l u e s a t z e r o c o n c e n t r a t i o n o f c e riu m were ^ o u n d .
t h r e e p o t e n t i a l s were found to conform to th e e q u a t i o n
y^a+bx+cx2

.

x the p o t e n t i a l s
a a 1.4626,

When y s l

(15°),

0 (25°),

in in c re a sin g o rd er,

in term ed iate v alues

p l o t t e d w ith the e x p e rim e n ta l v a lu e s
e q u a t i o n was f i t t e d

(3 5 °), and

From t h i s e q u a t i o n a n d

o f x were fo u n d ,
(F ig.

3),

and were

An e m p i r i c a l

t o t h e s e data*.

E = 1 .8 6048 - 0.002405T
From t h i s

type:

th e c o n s t a n t s were ;

b a 0.00265, and c = 0 .0 0 0 3 5 .

these c o n s ta n ts ,

and -1

These

0.00000359T 2

e q u a tio n v a lu e s o f the te m p e ra tu re c o e f f i c i e n t ,

dE
^

were c a l c u l a t e d a t 1 5 ° , 2 5 °, and 3 5 ° C . :
rili1
- . 0 0 2 4 0 5 •+• 2 ( . 0 0 0 0 0 3 5 9 T)
From t h e G i b b s - H e l m h o l t z e q u a t i o n :
-

Hote 2 .

a

R=

n f (e

S ince the a c t i v i t i e s

a r e n o t kn own,

- T

o f the cero u s and c e r i c

i t m u s t be a s s u m e d t h a t t h e s e a c t i v i t i e s

p r o p o rtio n a l, to the c o n c e n tr a tio n s
valency.

ions

C e 'l , (c')

and

Ce""(c*)

i n t h e two s t a t e s
w ill,

th erefo re,

are

of
be

i n t e r p r e t e d a s t h e t o t a l c o n c e n t r a t i o n s ox c e r i u m i n t h e
t r i v a l e n t and q u a d r iv a le n t form s,
in m illim oles

resp ectiv ely ,

expressed

o f c e riu m p e r th o u s a n d grams o f s o l u t i o n .

t

-

15

-

d e te rm in e d e x p e rim e n ta lly
c a l c u la te d from e q u a tio n

35
l.Uol
E (v o lte )
F ig .

T e m p e ra tu re - p o t e n t i a l c u rv e a t zero
c o n c e n tr a tio n o f c e r iu n .

J

-

values

o f - AH a t t h e

16

three

-

t e m p e r a t u r e s and z e r o c o n c e n t r a ­

ti o n of cerium in 0 .5 form al s u l f u r i c
f o r t h e r e a c t i o n C e , , l , -v-e —^ C e ' ' * .
equation

a c i d were c a l c u l a t e d
Prom t h e f r e e

energy

:

-AF - ENF
v alues

o f - A F v/ere c a l c u l a t e d f o r

t h e same r e a c t i o n .

EXPERIMENTAL DATA AND DISCUSSION
From t h e d a t a . o f t h e i n d i v i d u a l c e l l s
ticed

th at

in c e r t a i n

cases

i t may h e n o ­

the p o t e n t i a l o f the c e r i c -

c e r o u s e l e c t r o d e d r i f t e d downwar d o v e r a p e r i o d
I t was d e t e r m i n e d

by a n a l y s i s

th a t th is decrease

was t h e r e s u l t o f a c h a n g e t a k i n g p l a c e
cell,

w hich i s

of tim e.
in p o te n tia l

in the cerium h a l f ­

e x p r e s s e d by t h e r e a c t i o n C e ' 1 1 ' + e —> C e , f ' .

This change a l t e r e d

the c e r i c - c e r o u s r a t i o ,

a low ering of the p o t e n t i a l .

and thus caused

The m a g n i t u d e

of th is p oten ­

t i a l d r i f t , was r a r e l y g r e a t e r t h a n 0 . 0 1 m i l l i v o l t p e r h o u r ,
a n d was u s u a l l y much l e s s .
a c e l l in c re a se d d u rin g

I n a few c a s e s

the f i r s t

the p o t e n t i a l of

few h o u r s ;

th is,

however,

was d u e t o t h e f a c t t h a t t h e h y d r o g e n e l e c t r o d e h a d n o t
y e t come t o e q u i l i b r i u m .
The f i n a l p o t e n t i a l o f e a c h c e l l was c a l c u l a t e d f r o m
the v a lu e re c o rd e d im m ediately b e fo re a n a l y s i s ,
su lts

of the a n a l y s is .

the f a c t

The c o n s i s t e n c y

of the r e s u l t s

and

t h a t t h e f i n a l v a l u e s c o u l d be a c c u r a t e l y r e p r o ­

duced a f t e r v a ry in g p e rio d s
varied

and th e r e ­

slig h tly ,

ju stified

of tim e,
th is

and w i t h r a t i o s w hich

treatm ent of r e s u lts .

The

-

tim e
(h»u)
22
23
25
26.5
39
40
41
68
71
72

C e l l No. 1
temp.
b a r . p.
co rr.to
(°o.)
0 C,
740.1
15
739.7
739.1
739.1
25
735.7
735.6
735.0
35
728.8
732.0
733.1.

17

-

Ce e l e c t r o d e No. I
press.
E
E o bws .
c o rr'n .
c o rr.to
(E)
760 mm.
0.00051
1.46041
1.46092
0.00052
1.46038
1.46090
0.00052
1.46035
1.46087
0.00052
1 . 4 6035 1 . 4 6 0 8 7
0.00080
1.45712
1.45792
0.00080
1.45710
1.45790
0.00081
1.45708
1.45789
0.00128
1.45401 1.45529
1.45405
0.00123
1.45528
1.45405
1.45527
0 .0 0 1 2 2

E

1.4558

A n aly sis

of cerium s o l u t i o n
■before f i l l - a f t e r m e a s ing c e l l
ur.ing c e l l
10.055
9.862
Ce ’ ' '
9.855
. 9.981
Ce'’ ’ ’
1^910
19.843
Ce' ' ’ + Ce' ' "
1.020
1.012
C e ’ .' ' / C e ' " '
0
.00860
'lo g
0
.00052
co rrectio n

tim e
(hrs)'
22
23
26.5

C e l l No. 2 .
tem p.
bar. p.
co rr,to
(°C.)
0°C.
15
740.1
739.7
739.1

Ce e l e c t r o d e No. I l l
press.
E
corr.-to
•®obs.
•c o r r ' n .
760 mm.
(E)
1.46078
1
.
4
6
0
2
7
0.00051
1.46078
1
.
4
6
0
2
6
0.00052
1.46092
1.46040
0.00052

A n a ly s is o f cerium s o l u t i o n
b e f o re f i l l - a f t e r measing c e l l
u rin g c e l l
Ce'"
9.862
9.985
C e " "
9.981
9.853
Ce " ' + Ce * " *
19.843
19.838
Ce ' " / Ce " "
1.012
1.013
log
0.00561
co rrectio n
0.00032

E0

1.4612

t/i^m e \
(hrs)
22
23
26. 5
39
40
41

C e l l No. 3
tem p.
b ar. p.
(°C. )
co rr.to
0°C.
15
740.1
739.7
739.1
25 •
735.7
735.6
735.0

Ce e l e c t r o d e No. IV
press.
E
c o r r ’n.
®obs.
co rr.to
(E)
760 mm.
0.00051
1.46027
1.46078
1.46026
0.00052
1.46078
0.00052
1.46040
1.46092
0.00080
1.45702
1.45782
0.00080
1.45700
1.45780
0.00081
1.45698
1.457S9

E '

1.4582

A n a ly s is o f cerium s o l u t i o n
b e f o r e f i l l - a f t e r measing c e l l
u rin g c e l l
9.862
Ce • "
9.988
Ce' ' ' ’
9.981
9.858
C e 1 • 1 + Ge ' * 1 *
19.8.46
19.843
Ce • ’ ' / Ce « • • •
1.013
1.012
0.00561
log
0.00032
co rrectio n

time
(hrs)
1.5
18.5
19.5

C e l l No.' 4
tem p.
bar. p.
( °C. )
co rr.to
0°C.
' 15
739.0
733.8
734.1
A n aly sis

Ce e l e c t r o d e E o . I
press.
E
E obs
co rr,to
c o r r ’n.
760 mm.
(E)
1.46126
1.46073
0.00053
1.46138
1.46076
0.00062
1.46136
1.46076
0.00060

o f cerium s o lu t i o n
b e fo re f i l l - a f t e r measu rin g c e l l
ing c e l l
7.980
7.962
Ce* "
7.881
7.879
Ce ' ' ' »
15.861
15.841
Ce »' ' + Ce " 1 '
1.011
1.013
Ce 1 ’ ’/ Ce * ' » •
0.00561
log
0.00032
co rrectio n

E,

1.4617

-

tim e
(hrs)
14
14.5
15
16
22.5
23
25.5
29
39
40
41
42
43.5

C e l l No. 5
tem p.
b a r . p.
( °C. )
co rr.to
0°C.
35
738.0
737.6
737.8
737.3
15
735.2
735.2
735.9
737.9
25
739.8
7 40 10
740.1
740.4
740.4

19

-

Ce e l e c t r o d e No. I I
press.
E
c o r r ’n.
®obs.
co rr.to
760 mm.
(E)
0 .0 0 1 1 0
1.45407
1.45517
0 .0 0 1 1 0
1.45414
1.45524
0 .0 0 1 1 0
1.45414
1.45524
0 .0 0 1 1 1
1.45414
1.45525
0.00056
1.45997
1.46053
0.00056
1.46005
1.46061
0.00055
1.46038
1.4-6093
0.00051
1.46061
1.46102
0.00070
1.45783
1.45853’
1.45776
1.45846
0.00070
1.45776
1.45846
0.00070
0.00069
1.45849
1.45780
1.45850
0*00069 1 .4 5 7 8 1

A n a ly s is of cerium s o lu t i o n
b e f o r e f i l l - a f t e r measing c e l l
uring c e l l
8 .'085
8.067
Ce’ • •
7 . 960
7.969
Ce' 1"
1 6 . '045
16.036
- Ce ' ’ • +~Ce * * • •
1 . 016
Ce 1 * * / Ce ’. ’ * 1
1 .0 1 2
0 . 00689 ; '
log
0 . 0 004 0 J
co rrectio n

tim e
(hrs)
4
6
22.5
23
23.5
28.5
30
46.5
47
47.5

C e l l No. 6
temp.
b a r . p.
( °C. )
c o rr.to
0°C.
734.4
35
734.1
736.4
736.3
736.3
735.1
25
734.5
733.0
732.9
732.8

Ce e l e c t r o d e No. I l l
press.
E
TP
co rr.to
•^obs.
c o r r ’n.
760 mm.
(E)
1.45634
1.45514
0 .0 0 1 2 0
1.45626
1.45505
0 .0 0 1 2 1
1.45625
1.45507
0.00118
1.4-5509 1 . 4 5 6 2 7
0.00118
1.45626
1.45508
0.00118
1.45867
1.45784
.0.00083
1.45868
1.45784
0.00084
1.45776
1.45862
0.00086
1.45777
1.45863
0.00086
1.45862
1.45777
0.00085

A n a ly sis of cerium s o l u t i o n
b e f o r e f i l l - a f t e r measurin g c e l l
ing c e l l
8.010
8.057
C e '« *
7.968
7.965
Ce • ’ • *
15.978
16.022
Ce ’ ' ' +-Ce* • 1 *
1.005
1.0115
C e' ' ' / Ce'» f •
0
.00217
log
0.00013
correction

E0

1.4589

0.v.W

E0

1.4588

-

tim e
(hrs)
4
6
22.5
23
23.5

C e l l No. 7
temp.
h a r. p.
co rr.to
( °C. )
0°C.
734.4
734.1
736.4
736.3
736.3

20

-

Ce e l e c t r o d e No. IV
press,
E
c o r r *n .
•®obs.
c o rr.to
(E)
760 mm.
0.00120
1.45515
1.45635
0.00121
1.45508
1.45629
0.00118
1.45511
1.45629
0.00118
1.45514
1.4-5632
0.00118
1.45511
1.45629

E,

1.4565

A n a l y s i s o f Cerium s o l u t i o n
b e f o re f i l l - a f t e r measing c e l l
uring c e l l
Ce'”
8.057
8.030
Ce” ”
7.965
7.972
Ce ” * Ce ” ”
16.022
16.002
C e ” ’/ C e ” ”
1.0115
1.007
log
0.00303
. 3 '/£
co rrectio n
0.00018

tim e
(hrs)

Ce 11 No. 8
tem p.
bar. p.
( ° c . ) c o r r . to

0° C.

18.5
19
21
23
42 .5
66
67
68
69.5
70.5
71.5
88
89

25
15 .

35

745.4
744. 6
744.1
742.6
734.1
741.8
741.5
740.5
740.1
739.8
739.4
742.1
742.1

Ce e l e c t r o d e No. I
press.
E
co rr.to
E_
Eobs.
c o r r ' n.
760 mm.
0
(E)
1.45903
0.00060
1.45843
1.45904
1.45842
0.00062
0.00062
1.45842
1.45904,
1.46186
1.46141
0.00045
1.46164
1.46104
0.00060
1.46151
1.46105
0.00046
1.4-6106 1 . 4 6 1 5 3
0.00047
1.46148
1.46100
0.00048
1.45661
1.45555
0.00106
1.45637
1.45532
0.00107
1.45618
0.00107
1.455L1
1.45582
0 .0 0 1 0 2
1.45480
1.4-5581•- 1 . 4 5 7 2
1.45479
0 .0 0 1 0 2

A n a ly s is of cerium s o l u t i o n
b e f o re f i l l - a f t e r measing c e l l
u rin g c e ll
Ce'”
6.037
6.228
Ce” ”
5.985
5.914
Ce” , + Ce” ”
12.022
12.141
Ce ' ” / Ce ”
”
1.009
1.053
log
0.02243
co rrectio n
0.00137

('

-

tim e
(hrs)
18.5
19
21
23
42. 5
66
67
68
69.5
70.5
88
89

C e l l Ho. 9
temp.
b a r. p.
( °C. )
co rr.to
0°C.
25
745.4
744.6
744.1
15
742.6
734.1
741.8
741.5
740.5
35
740.1
739.8
742.1
742.1

21

-

Ce e l e c t r o d e Ho. I I
press.
E
corr'n.
®obs.
co rr.to
(E)
760 mm.
0.00060
1.45915
1.45855
0.00062 1.45853
1.45915
0.00062 1.45856
1.45918
0.00045 1.46155
1.46200
0.00060
1.46125
1.46185
0.00046
1.46185
1.46139
0.00047
1.46140
1.46187
0.00048 1.46137
1.46185
0.00106 1 .4 5 5 8 8
1.45694
1.45688
0.00107
1.45581
1.45646
0 .0 0 1 0 2
1.45544
1.45651
0 .0 0 1 0 2
1.45549

E,

A n a ly s is of cerium s o lu t i o n
b e fo re f i l l - a f t e r measing c e l l
u ring c e l l
6.121
6.037
Ce " ’
5.961
5.985
Ce » ' 11
12.082
12.022
Ce ' 1 * ■+■C e ’ »' *
1.027
1.009
Ce " » / Ce • »»«
0
.01157
log
o
. 00070
co rrectio n

tim e
(hrs)
18.5
19
21
23
24
4 2.5
67
68
69.5
89
93

C e l l Ho. 10
tem p. , b a r . p .
(°c.) c o r r . t o
0°C.
25 .
745.4744.6
744.1
742.6
15
742.1
734.1
741.5
740.5
740.1
35
742.1
741.7
-

Ce e l e c t r o d e Ho. I l l
press.
E
c o rr.to
^obs.
c o r r ’ n.
760 mm.
(E)
1.45913
1.45853
0.00060
1
.45913
1
.
4
5
8
5
1
0.00062
1
.45916
1.45854
0.00062
1
.
46205
0.00045 1.46160
1
.
46204
0.00046
1.46158
1.46183
1.46123
0.00060
1.46147
1.46100
0.00047
1.46182
1.46134
0.00048
1.45525
0.00106 1.45419
1.45653
0 .0 0 1 0 2 1 .4 5 5 5 1
1.45647
0.00103 1.45544

A n a ly s is o f cerium s o l u t i o n
b e fo re f i l l - a f t e r measing c e l l
u rin g c e l l
Ge1’ *
6.037
6.118
C e '" ’
5.985
5.959
C e 1• ' + Ce »1' •
12.022
12.077
Ce * ' • / Ce ' ’ • •
1.009
1.027
log
0.01157
co rrectio n
0.00070

E.

- 22 -

tim e
(hrs)

C e l l No. 12
temp.
b a r. p.
(°c.) c o r r . t o

0°c.
18.5
19
21
23
24
4 2 .5
68
69.5
89
93

25
15

35

745.4
744.6
744.1
742.6
742.1
734.1
740.5
740.1
742.1
741.7

Ce e l e c t r o d e Nq. IV
press.
E
c o r r 1n .
®obs.
co rr.to
(1 )
760 mm
0.00060
1.45841
1.45901
0.00062
1.45841
1.45903
1.4-5846 1 . 4 5 9 0 8
0.00062
0.00045
1.46150
1.46195
0.00046
1.46154
1.46200
C.00060
1.46117
1.46177
0.00048
1.46130
1.46178
0.00106
1.45402
1.45508
1.45646
0 .0 0 1 0 2
1.45544
1.45651
1.45548
0.00103

E0

1.4572

A nalyses o f cerium s o l u t i o n
b e f o re f i l l - a f t e r measing c e l l
u rin g c e l l
Ce* » •
6.037
6.107
C e1 ’ 1’
5.985
5.942
Ce 1 ' 14*
Ce ’’* '
12.022
12.049
Ce, , , / C e , , , ‘
1.009
1.028
log
0.01199
co rrectio n
0.00073

tim e
(hrs)
4
6
22.5
23
23.5
28.5
30
46 .5
47
47 .5

C e l l No. 13
b a r . ...p.
temp.
( ° c. ) c o r r . t o
0°C.
734.4
35
734.1
736.4
736.3
736.3
735.1
25
734.5
733.0
732.9
732.8

C e e e l e c t r o d e No. I
press.
E
Eobs.
co rr.to
c o rr'n .
760 mm.
(E)
1.45703
1.45583
0 .0 0 1 2 0
1.45689
1.45568
0 .0 0 1 2 1
1.45678
1.45560
0.00118
1.45683
1.45565
0.00118
1.45685
1.45567
0.00118
1.45925
1.45842
0.00083
1.45924
1.45840
0.00084
0.00086
1.45918
1.45832
1.45918
0.00086
1.45832
1.45917
0.00085
1.45832

A n a ly s is o f cerium s o l u t i o n
b e f o re f i l l - a f t e r measing c e l l
u rin g c e l l
Ce' ' *
6.005
6.008
Ce * ’ ' '
5.929
5.936
Ce * ' ' +• C e ' • ”
11.934
11.944
C e** ' / Ce' ' *1
1.013
1.012
lo g
0.00518
co rrectio n
.
0.00031

E.

1.4595

tim e
(hrs)
4
6
22.5
23
23.5

C e l l No. 14
Ce e l e c t r o d e No. I I
tem p.
b ar. p. press.
E
(°c.) c o r r . t o c o r r 'n .
®obs.
c o rr.to
0°C.
760 mm.
(E)
35
734.4
0 .0 0 1 2 0
1.45584
1.45704
734.1
0 .0 0 1 2 1
1.45570
1.45691
736.4
0.00118
1.45568
1.45686
736.3
0.00118
1.45569
1.45687
736.3
0.00118
1.45570
1.45688
A n a ly s is o f cerium s o l u t i o n
b e f o r e f i l l - a f t e r meas
ing c e l l
u rin g c e l l
C e11*
6.005
6.022
Ce’ " ’
5.929
5.931
Ce ’ ' ' + Ce ’ 1 1'
11.934
11.953
Ce » ’ ’/ C e 1 *»•
1.013
1.015
log
0.00647
co rrectio n
0.00040

tim e
(hrs)
8
12.5
21.5
23
23.5
41
50
51.5
73.5

C e l l No. 15
tem p.
bar. p.
( ° c. ) c o r r . t o
0°C.
35
742.3
742.9
25
744.9
744.7
744.7
15
745.2
744.9
744.3
740.5

Ce e l e c t r o d e N o . . I l l
press.
E
co rr.to
®obs.
c o rr'n .
760 mm.
(E)
1.45782
1.45680
0 .0 0 1 0 2
1.45781
1.45680
0 .0 0 1 0 1
1.45992
0.00061
1.45931
1.45991
1.45929
0.00062
1.45989
1.45927
0.00062
1.46254
1.46214
0.00040
1.46196
1.46237
0.00041
1.46234
0.00042
1.46192
0.00048
1.46177
1.46225

A n a ly s is o f cerium s o l u t i o n
b e f o r e f i l l - a f t e r m eas^
ing c e l l
u rieg c e ll
C e1*1
4.028
4.096
C e’ *”
3.995
3.963
Ce ' 1' + Ce ’»»»
8.023
8.059
Ce » ' » / Ce »••
•
1.008
1.034
log
0.01452
co rrectio n
0.00083

- 2.4 -

tim e
(hrs)
8
12.5
21.5
23
23.5
41
50
51.5
73.5

C e l l Ho. 16
tem p.
b a r . . p.
( °c. ) c o r r . t o
0°C.
35
742.3
742.9
25
744.9
744. 7
744.7
15
745.2
744.9
744.2
740.5

Ce e l e c t r o d e Ho. IV
press.
E
Eobs.
c o rr'n .
co rr.to
760 ram.
(E)
0 .0 0 1 0 2
1.45685
1.45787
0 .0 0 1 0 1
1.45686
1.45785
0.00061
1.45948
1.46009
0.00062
1.45948
1.46010
0.00062
1.45945
1.46007
0.00040
1.46241
1.46281
1.46229
0.00041
1.46269
1
.
4
6
2
2
5
0.00042
1.46267
0.00048
1.46212 1.46260

1.4631

A n a ly s is o f cerium s o l u t i o n
b e f o r e f i l l - a f t e r measing c e l l
u rig g c e l l
Ce " '
4.02S
4.063
C e""
3.995
3.984
Ce' 1' ^
Ce " "
8.023
8.047
Ce " • /
Ce" "
1.008
1.020
log
0.00860
co rrectio n
0.00049

tim e
(hrs)
1.5
2
2 .5
4 .5
10
10.5
18
19
20
22
23.5

C e l l Ho. 17
tem p.
b ar. p.
(°c.) c o rr.to
0°C.
35
738.9
738.5
738.0
737.5
735.6
735.4
734.0
25
734.0
734.4
734.6
15
734.6
A nalysis

Ce e l e c t r o d e Ho. I l l
press.
E
TP
co rr.to
c o rr'n .
obs.
760 mm.
(E)
1.45786
1.45676
0 .0 0 1 1 0
1.45676
1.45787
0 .0 0 1 1 1
1.45785
O.OGW2. 1 . 4 5 6 7 3
e l & o t 13 1 . 4 5 6 6 9 1 . 4 5 7 8 2
1.45779
1.45662
0.00117
1.45777
1.45660
0.00117
1.45906
1.45989
0.00083
1
.
4
5
9
0
5
1
.45988
0.00083
1.45905
1.45987
0.00082
1.46274
0.00061
1.46213
0.00061
1.46212
1.46273

of cerium s o l u t i o n
b e f o r e f i l l - a f t e r measing c e l l
u rin g c e ll
4.026
4 . ' 055
Ce " '
4 .004
3 . 989
Ce 1 " i
8 . 044
C e " ' + Ce " "
8.030
1 . 017
Ce 1 " / Ce " "
1.005
0 . 0 0 7 3 2 r- '
log
0 . 00045
co rrectio n

1.4632

- 525 -

ti m e
(hrs)
16.5
17.5
18.5

C e l l No. 18
tem p.
b a r . p.
co rr,to
(°c.)
0°C.
15
742.5
742.3
742.3

Ce e l e c t r o d e No. I
press.
E
E .
c o rr'n .
obs.
c o rr.to
760 mm.
(1 )
0.00047
1.46220
1.46267
0.00047
1.46226
1.46273
0.00047
1.46226
1.46273

of cerium s o l u t i o n
b e f o r e f i l l - a f t e r measin g c e l l
u rin g c e ll
Ce * • '
4.015
4 . 021
C e ' •» t
3.938
3 . 942
Ce • ' ' +■ Ce ' »« •
7 . 963
7.953
Ce « ' ' / Ce *' ' '
1 .0 2 0
1 . 020
0 . 0086 0
:
’ lo g
co rrectio n
0 . 0004 9

E,

1.4632

A nalysis

tim e
(hrs)
16.5
17.5
18.5
24
34
36
38
39.5
41

C e l l No. 19
temp.
b a r. p.
c o rr.to
(°c .)
0°C.
15
742.5
742.3
742.3
741.8
25
738.9
738.2
737.7
736.5
736.1

Ce e l e c t r o d e No. I l l
press.
E
®obs.
co rr.to
c o r r ’ n.
(E)
760 mm.
1.46194
1.46241
0.00047
1.46190
1.46237
0.00047
1.46241
0.00047
1.46194
0.00069
1.45913
1.45982
1.45987
0.00074
1.45913
1.45984
1.45909
0.00075
1,45986
0.00076
1.45910
1.45907 1.45986
0.00079
1,45984
1.45905
0.00079

A n a ly s is of cerium s o lu t i o n
b e f o r e f i l l - a f t e r measurin g c e ll
ing c e l l
Ce ’ 1 *
4.015
4.018
Ce ' ’ ' 1- Ge ’ ’ ’ »
7.954
7.953
3.936
Ce »* * »
3.938
1.020
1.021
Ce * ' ' / Ce » ' 1 *
0.00903
log
co rrectio n
0.00053

i-

EQ

1.4604

7

- 26 ■-

tim e
(hrs)
16.5
17.5
18.5
24.0
34
36
38
39.5
41
47
58
60
62
64
65

C e l l No. 20
tem p.
b a r. p.
c o r r . to
( c .)
0°C.
15
742.5
742.3
742.3
25
741.8
738.9
738.2
737.7
736.5
736.1
35
. 733.5
730.2
731.5
731.7
732.3
732.6
A n aly sis

Ce ie l e c t r o d e No. IV
press.
E
E
c o r r 1n .
obs.
c o rr.to
760 mm.
(E)
0.00047
1.46193
1.46240
1.46188
0.00057
1.46235
1.46192
0.00047
1.46239
0.00069
1.45981
1.45912
1.45986
0.00074
1.45912
0.00075
1.45907
1.45982
0.00076
1.45910
1.45986
1.45907
1.45986
0.00079
1.45904
0.00079
1.45983
1.45637
1.45758
0 .0 0 1 2 1
1.45748
0.00127
1.45621
1.45746
0.00125
1.45621
1.45747
0.00124
1.45623
1.45625
1.45747
0 .0 0 1 2 2
1.45626
1.45749
0.00123

of cerium s o l u t i o n
b e f o r e f i l l - a f t e r meaaing c e l l
urin g c e ll
Ce” »
4.015
4.053
Ce” ”
3.938
3.929
Ce ” * + Ce ” ”
7.953
7.962
C e ’ ” / Ce *” T
1.020
1.026
log
0.01115
co rrectio n
0.00068

- 2.7 -

3
16
17
18. 5
20
22
40
41
45
46. 5
51
63
64. 5

C ell
temp.
(°G .)
15

25

35

i—
i
C\2
.
o

tim e
(hrs )

bar. p.
co rr.to
0°C.
734.6
737.6
738.6
738.8
739.0
740.6
746.1
745.3
742.6
741.7
740.7
741.2
741.3

Ce e l e c t r o d e No. I
press.
E
c o r r ’n.
®obs.
co rr.to
(E)
760 mm.
0.00061
1.45004
1.45965
0.00055
1.45012
1.45067
0.00054
1.45017
1.45071
0.00053
1.45018
1.45071
0.00053
1 . 4 5020
1.45073
0.00050
1.45020
1.45070
0.00061
1.44689
1.44750
1.44686
0.00063
1.44749
0.00068
1.44680
1.44748
0.00069
1.44680
1.44749
0.00090
ft.44373
1.44463
1.44461
0.00089
1.44372
0.00089
1.44371
1.44460

A n a ly s is o f cerium s o lu t i o n
before f i l l ing c e l l
Ce ' ’ ’
3.346
C e"”
1.965
Ce " ’ + Ce " "
5.311
Ce* " / C e " "
1.703
log
correction

tim e
(hrs)
3
16
17
18.5
20
22

a f t e r measu rin g c e ll
3.342
1.966
5.308
1.700
0.23045
0.01408

Ce e l e c t r o d e No. II
C e l l No. 22
temp.
bar. p.
press.
E
® obs.
co rr.to
( ° c. ) c o r r . t o c o r r ’ n .
760 mm.
0 ° C . ' (E)
1.45066
1.45005
734.6
0.00061
15
1.45068
1.45013
737.6
0.00055
1.45016
1.45070
738.6
0.00054
1.45071
1.45018
738.8
0.00053
1.45020
1.45073
0.00053
789.0
740.6
1.45019
1.45069
0.00050
A n a ly s is o f cerium s o l u t i o n
b e f o r e f i l l - a f t e r mea s
ing c e l l
urin g c e l l
C e"’
3.346
3.334
C e""
1.965
1.962
Ce ’ " + Ce ’ ’ "
5.311
5.296
C e " ’/ C e " "
1.703
1.699
log
0.23019
co rrectio n
0.01316

E
0

1.4587

tim e
(hrs)
3
16
17
18.5
22
40
41
45
4 6.5
51
63
64.5

C e l l No. 23
te m p .
b a r. p.
( °c. ) c o r r . t o
0°C.
15
734.6
737.6
738.6
739.0
740.6
25
746.1
745.3
742.6
741.7
35
740.7
741.2
741.3

Ce e l e c t r o d e No. I l l
press.
E
c o r r ’n .
®obs.
c o rr.to
(E)
760 mm.
0.00061
1.44999
1.45060
0.00055
1.45001
1.45056
0.00054
1.45006
1.45060
0.00053
1.45065
1.45012
0.00050
1.45011
1.45064
0.00061
1.44682
1.44743
0.00063
1.44680
1.44743
0.00068
1.44673
1.44741
0.00069
1.44674
1.44743
0.00090
1.44366
1.44456
0.00089
1.44364
1.44453
0.00089
1.44363
1.44452

A n a ly s is of cerium s o lu t i o n
b e f o r e f i l l - a f t e r m eas
ing c e l l
urin g c e ll
Ge” ’
3.346
3.337
C e * ' 1’
1.965
1.962
Ce ' ’ ’ + Ce ’ ” ’
5.311
5.229
Ce ’ ’ • / Ce ’ ' ' '
1.703
1.701
lo g
0.23070
co rrectio n
0.01410

tim e
(hrs)
3
16
17
18.5
20
22.
40
41
42
4 6.5

C e l l No. 24
tem p.
b ar. p.
(°C .)
co rr.to
0° C .
734.6
15
737.6
738.2
738.8
839.0
740.6
746.1
25
745.3
742.6
741.7

Ce e l e c t r o d e No. IV
press.
E
Eobs.
c o r r . to
c o r r ’n.
760 mm.
(E)
1
.45059
0.00061
1.44998
1.45058
0.00055
1.45003
1.45061
1.45007
0.00054
1.45064
1.45011
0.00053
1
.45066
1.45013
0.00053
1.45062
1.45012
0.00050
1.44745
1.44684
0.00061
1.44744
1.44681
0.00063
1.44674
1.44742
0.00068
1.44744
1.44675
0.00069

A n a ly s is o f cerium s o l u t i o n
b e f o r e f i l l - a f t e r measing c e l l
u rin g c e ll
Ge' ' *
3.346
3.346
C e '” '
1.965
1.977
C e '” + Ce” ”
5.311
5.323
C e ' ' ’/ Ce » ” ’
1.703
• 1.692
log
0•22840
correction
0.01351

E0

1.4610

- 25 -

tim e
(hrs)
8
12.5
21.5
23
23.5
41 .
50
51.5
73.5

C e l l No. 25
tem p. b a r . p.
(°C .) c o r r . t o
0°C.
35
742.3
742.9
25
744.9
744.7
744. 7
15
745.2
744.9
744.2
740.5

Ce e l e c t r o d e
press.
c o rr'n .
®obs.
(E)
0 .0 0 1 0 2
1.45666
0 .0 0 1 0 1
1.45720
0.00061
1.45987
1.45988
0.00062
0.00062
1.45987
1.46266
0.00040
0.00041
1.46256
0.00042
1.46253
0.00048
1.46233

No.

I
E
co rr.to
760 mm.
1.45786
1.45821
1.46048
1.46050
1.46049
1.46306
1.46297
1.46295
1.46281

E.

1.4641

A n a ly s is o f cerium s o l u t i o n
b e f o r e f i l l - a f t e r meas ing c e l l
u rin g c e l l
2 . 071
2.038
Ce 1 * »
1.991
Ce » ’ 1 t
1 . 971
4 . 042
4.029
C e ' ' ' + Ce » 1 1 '
1.024
1 . 051
C e 1 ’ » / Ce »' '»
0 . 02160
log
0 . 00128
correction

tim e
(hrs)
20
21
22
53
54
55
55.5
74.5
75.5
76.5

C e l l No. 26 .
"t/GJTip* b a r . p .
co rr.to
(°G .)
0°C.
742.0
15
742.1
742.1
737.9
25
737.8
738.2
738.1
737.7
35
737.7
738.3
A nalysis

Ce e l e c t r o d e No. I
press.
E
■R
obs.
co rr.to
EQ
c o r r ’n .
760
mm.
(E)
1.46353
1.46305
0.00048
1,46355
1.46307
0.00048
1.46355
1.46307
0.00048
1.46019
1.45945
0.00076
1.46034
1.45958
0.00076
1.45956
1.4 6 0 3 3 '
0.00077
1.46033
1.45955
0.00078
1.45809
1.45696
0.00113
1.45808
1
.
4
5
6
9
5
0.00113 •
1.45809
1.4596
1.45697
0 .0 0 1 1 2

of cerium s o l u t i o n
b e fo re f i l l - a f t e r measuring c e l l
ing c e l l
1.0343
•
1
.
0
3
3
1
Ce ’
0
.9776
0
.
9
7
9
4
Ce1
2
.0119
2
.
0
1
2
5
Ce ’ '» + Ce ‘ ' 1 '
,
,
/
Ce
t
i
»•
1
.058
1.055
Ce'
0
.02449
log
0.00150
co rrectio n

tim e
(hrs)
20
21.
22
53
54
55
55.5

C e l l No. 27
temp.
b a r . p.
(°C .)
co rr.to
0°C.
15
742.0
742.1
742.1
25
737.9
737.8
738.2
73S.1

Ce e l e c t r o d e No. I l l
press.
c o rr'n .
E obs.
co rr.to
(E)
760 mm.
0.00048
1.46297
1.46345
0.00048
1.46301
1.46349
0.00048
1.46301
1.46349
0.00076 .1 .4 5 9 5 7
1.46031
0.00076
1.45969
1.46045
0.00077
1.46045
1.45968
1.46046
0.00078
1.45968

Analysis of cerium solution

before f i l l ing cell

Ce" '
Ce ’ * ' 1
Ge 1 ' * -t Ce* ' ' '
C e ' " / Ce " "
log
co rrectio n

tim e
^hrs)

20
21
22

C e l l No. 28
tem p.
b a r . p.
C°c.) c o r r . t o
0°C.
15
742.0
742.1
742.1

1.0331
0.9794
2.0125
1.055

a f t e r measu rin g c e l l
1.0313
0.9754
2.0067
1.057
0.02407
0.00142

Ce e l e c t r o d e NO. IV
JS
press.
co rr.to
Eobs.
c o rr'n .
760 mm.
(E)
1.46343
1.46295
0.00048
1.46348
1.46300
0.00048
1.46348
1.46300
0.00048

Analysis of cerium solution
before fill- after measuring cell
ing cell

Ce’ t
C e ' i »r
C e ’ • + Ce * * 1 '
Ce ' ' / Ce • ' 1 •
log
co rrectio n

1.0331
0.9794
2.0125
1.055

1.0412
0.9872
2.0248
1.055
0.02325
,0.00133

E,

1.4619

- 31 -

tim e
(hrs}
13
14
15
18
20.5
21.5

C e l l No. 1A
temp.
b a r . p.
(°C .)
co rr.to
0°C.
15
749.7
749.4
749.0
747.2
746.7
746.6

Ce e l e c t r o d e No. I
press.
E
E Obs.
v
c o r r ’n .
co rr.to
(E)
760 mm.
0.00035
1.46264
1.46299
0.00035
1.46262
1.46297
0.00036
1.46277
1.46313
0.00039
1.46279
1.46318
0.00040
1.46285
1.46325
0.00040
1.46281
1.46321

A n a ly s is of cerium s o l u t i o n
b e f o r e f i l l - a f t e r meas
ing c e l l
u rin g c e l l
Ge* ' 1
5.901
5.878
Ce ' ’ ’ '
5.581
5.581
Ce ' ’ ' +
Ce' ’ ’ ' 11.482
11.459
C e ' • ' / Ce' ' "
1.057
1.053
log
0.02243 .
co rrectio n
0.00128

Time
(bars)
13
15
18
20.5
21.5
34.5
36.5
38
40
42
64
65
66

C e l l No. 2A
te m p .
b a r . p.
(°c.) co rr.to
0°C.
15
749.7
749.0
747.2
746.7
746.6
25
741.6
740.5
740.2
738.8
738.2
35
741.4
741.3
741.2

Ce e l e c t r o d e
press.
E
obs.
c o r r ’n .
(E)
1.46267
0.00035
0.00036
1.46278
1.46279
0.00039
1.46285
0.00040
0.00040
1.46283
1.45977
0.00070
1.45974
0.00071
1.45974
0.00072
1.45970
0.00074
1.45969
0.00076
0.00106
1.45711
0.00106
1.45705
0.00106
1.45708
.

No.

II
E
c o rr.to
Ew
o760 mm.
1.46302
1.46314 .
1.46318
1.46325
1.46323
1.46047
1.46045
1.46046
1.46044
1.46045
1.45817
1.4-5811
1.4596
1.45814

A n a ly s is of cerium s o l u t i o n
b e f o r e f i l l - a f t e r meas
ing c e l l
uring: c e l l
C e '"
5.901
5.899
G e ’ 111
5.581
5.571
Ce ’ * ’ + C e ' ’’ '
11.482
11.470
C e ’ »’/ C e ’ ’ ’ •
1.057
1.058
log
0.02449
co rrectio n
0.00150

tim e
(hrs)
13
20.5
21.5
34.5
36.5
38
39
40
42

C e l l Ho. 3A
tem p.
b a r. p.
( °c. ) c o r r . t o
0 °C.
15
749.7
746.7
746.6
25
741.6
740.5
740.2
739.2
738.8
738.2

Ce e l e c t r o d e No. I l l
press.
E
c o rr'n .
•®obs.
co rr.to
760 mm.
(E)
0.00035
1.46188
1.46223
0.00040
1.46315
1.46275
0.00040
1.46276
1.46316
0.00070
1.45966
1.46036
0.00071
1.45965
1.46036
0.00072
1.45966
1.46038
0.00074
1.46036
1.45962
0.00074
1.46034
1.45960
0.00076
1
.46035
1.45959

A n a ly sis of cerium s o l u t i o n
b e f o r e f i l l - a f t e r measing c e l l
u rin g c e l l
Ce’ ”
5.901
5.878
C e '” '
5.581
5.573
Ce ' ” + Ce ' ”
'
11.482
11.451
Ce ” ’/ Ce ’ ”
’
1.057
1.055
log
0.02325
co rred tio n
0.00137

tim e
(hrs)
.13 .
20.5
21.5
36.5
38
39
40
42
64
65
66

C e l l No. 4A
"fcdfljp • b a r . p .
(°C .)
c o rr.to
0°C.
15
749.7
746.7
746.6
. 740.5
25
740.2
739.2
738.8
738.2
741.4
35
741.3
741.2

IV
Ce e l e c t r o d e N o .
press.
E
E o ub s .
c o rr.to
c o r r 1n .
760 mm.
■(E)
1.46224
1.46189
0.00035
1.46316
1.46276
0.00040
1.46316
1.46276
0.00040
1.46038
1
.
4
5
9
6
7
0.00071
1.46038
1
.
4
5
9
6
6
0.00072
1
.46039
1.45965
0.00074
1
.46036
1.45962
0.00074
1
.
46037
1.45961
0.00076
1.45790
0.00106
1.45684
1.45686
1.45792
0.00106
0.00106
1.45793
1.45687

A n a ly sis o f cerium s o l u t i o n
b e f o r e f i l l - a f t e r measing c e l l
u rin g c e ll
Ce” '
5.901
5.891
Ce” ”
5.581
5.567
Ce ’ ” + Ce ” ”
11.482
11.458
Ce ’ ” /
Ce” ”
1.057
1.058
log
0.02449
co rrectio n
0.00150

E,

1.4-617

- 33 tim e
(hrs)

12
1 2.5
13
13.5
14

C e l l No. 5A
tem p.
b a r . p.
(°C .)
co rr.to
D°c
15
741.2
741.1
741.0
741.0
740.8

Ce e l e c t r o d e No. I
press,
E
E
c o r r ' n.
obs.
co rr.to
(E)
760 mm
0.00052
1.46227
1.46279
0.00052
1.46224
1.46276
0.00053
1.46222
1.46275
0.00053
1.46225
1.46278
0.00053
1.46226
1.46279

1.4647

A n a ly s is of cerium s o l u t i o n
b e f o r e f i l l - a f t e r measing c e l l
urin g c e ll
Ce’ "
0.995
1.005
Ce” "
0.927
0.929
Ce" • + Ce"
"
1.922
1.934
C e«" / G e "
"
1.073
1.082
lo g
0.034i|3
co rrectio n
0.00195

tim e
(hrs)
12
12.5
13
13.5
14
19.5
23
40 .5
41
41 .5
42
4 2.5
64.5
65
66
66.5

C e l l No. 6A
tem p.
b a r . p.
(°c.) c o r r . t o
0°C.
15
741.2
741.1
741.0
741.0
740.8
25
737.9
739.4
743.1
.743.0
742.5
742.3
742.1
741.1
35
741.0
740.4
740.3

Ce e l e c t r o d e No. I I
press.
E
Eobs.
co rr.to
c o r r 1n .
760 mm.
(E)
1.46216
1.46268
0.00052
1.46264
1.46212
0.00052
1.46265
1.46212
0.00053
1.46214
1.46267
0.00053
1.46268
1.46215
0.00053
1.45997
0.00079
1.45918
1.45993
1.4 -5913
0.00080
1.45962
0.00070
1.45892
1.45894
1.45964
0.00070
1.45963
0.00071
1.45892
1.45962
1.45891
0.00071
1
.45962
0.00072
1.45890
1
.
45718
0.00106
1.45612
1.45716
0.00106
1.45610
1.45604
1.45712
0.00108
1.45604
1.45712
0.00108

A n a ly s is of cerium s o l u t i o n
b e f o r e f i l l - a f t e r measing c e l l
urin g c e ll
Ce" ’
0.995
1.012,
Ce" "
0.927
0.916
Ce 1 " + Ce "
"
1.922
1.928
Ce * " / Ce "
"
1.073
1.105
lo g
0.04336
co rrectio n
0.00264

Eo
"

1.4598

- 34 -

tim e
(hrs)
12
12.5
13
13.5
14
19.5
23
40.5
41
41 .5
42
42.5

C e l l No. 7A
tem p.
bar. p.
co rr.to
(°G .)
0 c C.
15
741.2
741.1
741.0
741.0
7 4 0 . -8
25
737.9
739.4
743.1
743.0
742.5
742.3
742.1
A nalysis

Ce e l e c t r o d e
press.
c o rr'n .
®obs.
(E)
0.00052
1.46217
1.46216
0.00052
0.00053
1.46216
0.00053
1.46218
0.00053
1.46219
0.00079
1.45926
0.00080
1.45923
0.00070
1.45915
0.00070
1.45915
1.45913
0.00G71
1.45911
0.00071
0.00072
1.45911

No.

IV
E
c o r r . to
760 mm.
1.46269
1.46268
1.46269
1.46271
1.46272
1.46005
1.46003
1.45985
1.45985
1.45984
1.45982
1.45983

o f cerium s o l u t i o n
b e f o r e f i l l - a f t e r measing c e l l
u rin g c e l l
1,002
0.995
Ce « ' ’
0.923
0.927
Ce * 1 ’ 1
1.925
1.922
Ce ' 11 + C e ’ 1 1 '
1.086
1.073
Ce • ' ' / Ce » ' • 1
0,03583
log
0.00212
co rrectio n

I

Eo

1.4619

- 35 data fo r

the

in d iv id u al c e lls

The f i n a l v a l u e s

graph i t

r e c o r d e d on p a g e s

f o r the c e l l s

e e r i e ammonium s u l f a t e s
These d a t a a r e

are

c o n t a i n i n g c e r o u s and

are recorded

in T ables I , I I ,

expressed g ra p h ic a lly

in F ig .

From t h i s

i s e v i d e n t t h a t t h e p o t e n t i a l i s d e p e n d e n t upon t h e

to ta l con cen tratio n of eerie
Kunz ( K u n z ,

J.

a n d c e r o u s ammonium s u l f a t e s .

Am. Chem. S o c . , jxS,

the p o t e n t i a l o f t h i s

electro d e

c o n c e n t r a t i o n was p r a c t i c a l l y
cen tratio n

t r o d e was l o w e r .

96,

(1931))

in s u lf u r ic

He a l s o

acid of a fix ed

a.cid,

the p o t e n t i a l of the e l e c ­

A g r a p h o f Kunz* d a t a i s

shown i n F i g .

by t h e p r e p a r a t i o n

a t two w i d e l y s e p a r a t e d c o n c e n t r a t i o n s

of t o t a l

e q u a l to a p c ro x i'ra a te ly one,

using e e r ie

and c e ro u s s u l f a t e s

i n t h e a b s e n c e o f ammonium s u l f a t e ,

0 .5 form al s u lf u r ic

acid .

n itin g

some e e r i e ammonium s u l f a t e

to c o n v e r t to th e o x id e ,
acid

These s a l t s

w e r e p r e p a r e d by i g ­

s tro n g ly f o r s e v e ra l hours

and d i s s o l v i n g

i n "w ater.

P a r t o f t h e s o l u t i o n was r e d u c e d w i t h h y d r o g e n p e r o x i d e ,
evapoTfited s lo w ly to o b t a i n c r y s t a l s

and c e ro u s s u l f a t e s .
cells,

in

h eatin g w ith co n centrated s u lf u r ic

to c o n v e r t to th e s u l f a t e ,

bo th p o rtio n s

5.

to ta l co n cen tratio n

o f c e r i u m s u l f a t e s was f u r t h e r c o r r o b o r a t e d

the r a t i o

t o t a l con­

sh o w ed t h a t i n a h i g h ­

The i n d e p e n d e n c e o f t h e p o t e n t i a l o n t h e

cerium w ith

s how ed t h a t

in d ep en d en t of the

of cerium s u l f a t e s .

e r c o n c e n tra tio n of s u lf u r ic

of c e lls

4.

and I I I .

and

of eerie

T a b l e IY s h ow s t h e d a t a f r o m t h e s e

and they a r e e x p re s s e d g r a p h i c a l l y

A f t e r m easu rem en t and a n a l y s i s

in Fig.

of-these

6.

c e l l s was com-

- 36 -

Table
C e l l No.
2
4
11
15
16
17
18
22
25
28

I.

T o t a l Ce

Ce * ' ' / C e ' ' "

19.838
15.861
11.999
8.059
8.047
8.044
7.963
5.296
4.042
2.025

1.013
1.013
1.025
1.034
1 .0 2 0
1.017
1 .0 2 0
1.699
1.051
1.055

T able I I
C e l l No.
3
-5
6
13
19
24
27

T o t a l Ce

1
7
8
9
10
12
14
20
21
23
26

T o t a l Ce
19.855
16.002
12.142
1 2.081
12.077
12.049
11.953
7.962
5.308
5.299
2 .0 1 2

1.013
1.016
1.005
1 .0 1 2
1 .0 2 1
1.692
1.057

III

So

Scorr.
t o 760 mm.
1.4609
1.4614
1.4618
1.4623
1.4626
1.4627
1.4627
1.4507
1.4628
1.4635

1.4612
■1.4617
1.4624
1.4631
1.4631
1.4632
1.4632
1.4639
1.4641
1.4649

. , .^ c o rr.
tQ 760 mm.

So

1.4579
1.4585
1.4586
1.4592
1.4598
1.4474
1.4605

1.4582
1.4589
1.4586
1.4595
1.4604
1.4610
1.4619

•“■ c o r r .
t o 760 mm.
1.4553
1.4563
1.4558
1.4565
114565
1.4565
1.4569
1.4575
1.4446
1.4445
1.4581

S0

(25°C .)

Ce ' • ' / C e

19.846
16.045
15.978
11.944
7.954
5.323
2.007

Table
C e l l No.

(15°C .)

(35°C .)

Ce ' ' ' / C e ’ ' ’ '
1 .0 2 0
1.007
1.053
. 1.027
1.027
1.028
1.015
1.026
1.700
1.701
1.058

1.4558
1.4565
1.4572
1.45721.4572
1.4572
1.4573
1.4582
1.4587
1.4586
1*4596

— -37 —

it

t.
i;
10

1

F i g , ii.
Concentre lio n - p o t e n t i p l cu rrp p of
e e r i e - c e r o u s Gtumanivsb p u l f f i t e c e l l p r-1 1;3C , £?50 >
35-'J C.
i n 0 , 5 forui/».l s u l f u r i c e c i d .

•

i

f:

,

uu?

.

*)*M
H»♦

I , ^ to

i. \voU?;
I’ itf:. f-,

C o n c e n t r e t i o n - p o t e n t i a l curve? of e e r i e p u l f p t * c e l l s ( Kun? ) fi t ?K°C, i n 1 , 0 e n d 0.
pulfuric acid,

T a b l e IV
C e l l No.

tem p.

T o t a l Ce

Ce • ' ' / C e " » '

1A
5A

15

11.459
1.934

1.053
1.082

® corr.
t o 760 mm
1.4632
1.4628

3A
7A

25

11.451
1.925

1.055
1.086

1.4604
1.4598

1.4617
1.4619

2A
4A
6A

35

11.470
11.458
1 .928

1 .058
1.058
1.105

1.4581
1.4581
1.4571

1.4596
1.4596
1.4598

E0
1.4645
1.4647

T able V
T o t a l Ce c o n c e n t r a t i o n
11.482
time
a d d i t i o n s to
(hrs)
electro d e II
none
8
0 . 0 7 5 g . HH/,;4 I 2 ? ° 4
26
0.075g.
55
) 2 S 04
12 d r o p s c o n c . H2 SO4
72

Ce ' » ' / C e " ' 1
1.05
electrod e
II
1.45696
1.45706
1.45493
1.45681
1 .4 56 4-3 1 . 4 5 2 7 3
1.45088
1.45629

drop in E
0.00178
0 .0 0 1 8 2
0.00171

T a b l e VI
- a H and - a F f o r the r e a c tio n
C e 1 ' ' ' * e —» C e ' ' '
in 0 .5 f s u lf u r ic a c id a t d if f e r e n t tem peratures.
te m p .
(°C.)
15
25
35

E '
(v o lts)
1.4656
1.4626
1.4603

dE
dT
0.000337
0.000265
0.000194

-A H
(c a l.)
36,033
35,547
35,050

- a ?
(cal.)
33,795
33.726
33,673

- 40 -

li

a

t:C)

1

, ^60

E (volte)

6. C o n c e n t r a t i o n - p o t e n t i a l carver- o f c e r t c - s e r o u s ?u*i~
f e t e c e l l 6 e t I ? 0 , ? 5 ° , end 35°* - r- 0*5 fcroi el s u l f u r i c ecid^-

A

- 41 -

p leted,

two o f t h e c e r i u m h a l f - c e l l s

s o l u t i o n in w hich th e

were r e f i l l e d

t o t a l c o n c e n t r a t i o n o f c e r i u m was 11.48i3

m i l l i m o l e s p e r th o u s a n d grams o f s o l u t i o n .
to e q u i l i b r i u m ,
calcu lated

w ith, t h e

a quantity

When t h e y h a d come

o f s o l i d ammonium s u l f a t e

(O.OVbgi!)

to be e q u a l to th e q u a n t i t y w h ich would h av e oeen

p r e s e n t had the s o l u t i o n

o rig in ally

b e e n . p r e p a r e d from e e r i e

an d c e r o u s ammonium /s u l f a t e s , was a d d e d t o t h e s o l u t i o n
o f th e cerium h a l f - c e l l s .
d i s s o l v e d and d i s t r i b u t e d
cell

When t h e s o l i d was c o m p l e t e l y
th ro u g h o u t the s o l u t i o n in the h a l f ­

(when t h e p o t e n t i a l h a d c e a s e d t o v a r y ) ,

a d d i t i o n was m a d e .

E q uilibrium values

a c i d was a d d e d t o

of p o te n tia l

760 mm. p r e s s u r e

a r e r e c o r d e d i n T a b l e V.

may b e s e e n t h a t

the a d d i t i o n of s u l f a t e

low ers the p o t e n t i a l of the c e r i c - c e r o u s
b e a d d e d a s ammonium s u l f a t e

tra tio n

electrode

Erom t h e s e d a t a i t
io n to the s o l u t i o n
electro d e,

Since

in s u lf u r ic

the

c o r r e c t e d to

or s u lf u r ic acid .

o f t h i s b e h a v i o r may be a s f o l l o w s :
the c e r i c - c e r o u s

another equal

When e q u i l i b r i u m was a g a i n e s t a b l i s h e d ,

tw elve d ro p s o f c o n c e n tr a te d s u l f u r i c
h alf-cell.

i n one

w hether i t

The e x p l a n a t i o n

the p o t e n t i a l of

acid

of a fix ed

concen­

i s d e p e n d e n t upon th e r a t i o
C e 1" ( c 1 X a * )
C e " ' ’ (c« X a w)

( a ’ and a ” b e in g

the a c t i v i t i e s

resp ectiv ely ), i t
its

influence

activ ities

is

of the e e r i e

p ro b a b le t h a t the s u l f a t e

on t h e p o t e n t i a l b y e f f e c t i n g

o f one o r b o t h o f t h e s e

s ta te d previously ,

and c e r o u s i o n s ,

is a decrease

ion e x e r c is e s

a change' i n th e

two i o n s .

in p o t e n t i a l ,

The e f f e c t ,
which i s

as

caused

- 42 -

by a n i n c r e a s e

in the above r a t i o .

b e D r o u g h t a b o u t by e i t h e r
increasin g
creasin g

the a c t i v i t y

the a c t i v i t y

o r D o th o f two c h a n g e s :

o f the c ero u s ion;

of the e e r i e

t o be t h e more p r o b a b l e ,

sin ce

t o h y d r o l y z e and form co m p lex es
-that o f t h e c e r o u s

r a t i o ' i n c r e a s e may

This

the

.ion.

first,

and. s e c o n d .,

by

by d e ­

T h is l a t t e r seems

ten d en cy o f the e e r i e

i s much m o re p r o n o u n c e d

ion
than

io n . '

The c h a n g e i n p o t e n t i a l w i t h r e s p e c t t o t o t a l c o n c e n ­
tra tio n

o f c e r i u m i n t h e w o r k o f Kunz a n d i n

work c o m p a r a b le

to h i s ,

o p p o site d ir e c tio n .

is

s l i g h t in both c a s e s,

A ccording

t o K unz,

fo rm al a c id d e c re a se d 0 .8 m i l l i v o l t s

c o n c e n tra tio n range,
T his d i f f e r e n c e
sm aller,

as

the c o n c e n t r a t i o n o f
of cerium p e r th o u ­

I n th e p r e s e n t work,

o v e r t h e same

the p o t e n t i a l in c re a s e d 0 .3 m i l l i v o l t s .

in d ir e c tio n

however,

b u t in

t h e p o t e n t i a l i n O. b

c e r i u m d e c r e a s e d f r o m 11 t o 0 m i l l i m o l e s
san d grams o f s o l u t i o n .

th a t p a rt of th is

o f change w ith c o n c e n tr a tio n is

th an th e d i f f e r e n c e betw een the f i n a l v a lu e s

a t 2 5 ° C. when e x t r a p o l a t e d

to z e ro c o n c e n t r a t i o n of cerium ,

Kunz' v a l u e b e in g 1 .4602 v o l t s ,

and t h a t of t h i s e x p e rim e n t,

1.4620 v o l t s .
At z e ro c o n c e n t r a t i o n o f e e r i e
fates,

a n d c e r o u s ammonium s u l ­

t h e e f f e c t o f t h e ammonium s u l f a t e a s w e l l a s

t h e j u n c t i o n p o t e n t i a l s h o u l d become z e r o ,
tio n

of the curves

in F ig.

4 g ives

t i o n p o t e n t i a l of' th e c e r i c - c e r o u s
su lfu ric

acid a t

15°,

25°,

t h a t o£

so th e e x t r a p o l a ­

the normal o x id a tio n - r e d u c electro d e

and 35° C .,

in 0 .5 form al

m easured*against a

- 43 -

h y d r o g e n e l e c t r o d e a t 2 5 ° C . a n d 760 mm. o f m e r c u r y i n 0 . 5
form al s u l f u r i c
It

acid .

s h o u ld be n o te d

th a t w hile

t i a l a t zero co n ce n tra tio n

th e v a lu e s f o r the p o te n ­

o f c e r iu m o b t a i n e d from m e a s u re ­

m e n t s o f t h e c e r i u m ammonium s u l f a t e
cerium s u l f a t e
eratu re

cells

d iffer

co efficien ts

w ith in the l i m i t s
The v a l u e s
co n ten t

cells,

and t h o s e from t h e

by a p p r o x i m a t e l y . 0 . 5 m v . ,

f o r the

two g r o u p s o f c e l l s

are

the

te m p ­

id en tical,

of ex perim ental e r r o r .

of free

en e rg y d e c r e a s e and d e c r e a s e i n h e a t

( - A F a n d - AH) r e c o r d e d

i n T a b l e VI a r e l a r g e ,

as

w o u l d be e x p e c t e d f r o m a s y s t e m w i t h s u c h a h i g h p o t e n t i a l .
The f a c t t h a t t h e
C e , , , , +e

free

Ce, , ,

energy d e c re a se

is p o sitiv e,

for

denotes

the r e a c t i o n

that

the r e a c t i o n

w i l l proceed spontaneously

in the d i r e c t i o n

of the e q u a tio n .

The f a c t

in h e a t c o n te n t is g r e a te r

\
free

th at

the d e c r e a s e

energ y decrea.se,

denotes

as the r e a c t i o n p ro c e e d s.
m ined c a l o r i m e t r i c a l l y

th a n the

t h a t the system g iv e s o f f h e a t

V alues f o r

th is

r e a c tio n as d e t e r ­

a re n o t a v a i l a b l e a t the p r e s e n t tim e.
SUMMARY

1.

The o x i d a t i o n r e d u c t i o n - p o t e n t i a l o f t h e c e r i c - c e r o u s

electro d e

in 0 .5

form al s u l f u r i c

a c i d has been d e t e r m in e d ' a t
I
r e f e r e e d to a hydrogen e le c tr o d e in
.

th ree tem p eratu res.
0 .5 form al s u l f u r i c
values are:
1.4603 v o l t s .

at

a c i d a t 760 mm. p r e s s u r e a n d 2 5 °

15° - 1 . 4 6 5 6 ;

a t 25° -1 .4 6 2 6 ;

a t 35

- 44 -

2.

The e f f e c t o f ammonium s u l f a t e

p o t e n t i a l of the c e r ic - c e r o u s

or s u lf u r ic

electrode is

a c i d on t h e

to decres.se th e

p o t e n t i a l of the e l e c tr o d e .
3.

The . t e m p e r a t u r e c o e f f i c i e n t o f t h e e l e c t r o d e h a s

determ ined, a t th re e
0.00033;

a t 25°

tem p eratu res.

- 0.00027;

been

The

v a l u e s a r e a t 15°

a t 35° -

0.00020 v o l t s p e r

' -

d eg ree..
4.

The d e c r e a s e

C e, , , 1 +e —>

C e 111

The v a l u e s a r e :

in h e a t c o n ten t

( - AH) f o r t h e r e a c t i o n

has been d eterm in ed a t

a t 15° - 3 6 , 0 3 3 c a l . ;

three

tem peratures.

a t 25° - 35,547 c a l . ;

a t 3 5 ° - 3 5 , 0 SO c a l .
5.

The f r e e

en erg y decrea.se

has been determ ined a t

th ree

at- 15° - 3 3 , 7 9 5 c a l . ;

a t 25°

Cdili

( - AS1)

f o r th e.ab o v e r e a c tio n

te m p e ra tu re s .The-values
- 33,
*

726 c a l . ;

are:

a t 35° - 33,6 7 3